Focal plane arrays (FPAs) that detect infrared (e.g., thermal) radiation are used by infrared cameras to provide thermal images. For example, thermal radiation passing through an optical path of an infrared camera is received by infrared detectors of the FPA, which provide image data for pixels of thermal images.
The quality of thermal images provided by FPAs may be degraded due to non-uniform responses among the individual infrared detectors to incident infrared radiation. Because the magnitude of the non-uniformity may be large in comparison to the magnitude of the actual response due to the incident infrared radiation, various techniques are typically used to compensate for the non-uniformity and obtain a desirable signal-to-noise ratio.
For example, in some conventional infrared imaging devices, the FPA may be calibrated over one or more levels of photon flux by inserting a mechanical shutter that can selectively be moved into the optical path of the infrared camera. The FPA takes one or more data frames or snapshots of the shutter to calibrate its response, and the collected data may then be used to calibrate the FPA to provide a more uniform response. Such a mechanical shutter may also be found in some non-thermal (e.g., visible light) imaging devices having charge-coupled devices (CCDs) or complementary metal-oxide (CMOS) sensors, for example, for calibration and/or imaging capturing purposes.
However, a mechanical shutter requires a shutter blade (e.g., a shutter paddle), an actuator (e.g., a motor) and an associated drive train to move the shutter blade in and out of the optical path. As such, a mechanical shutter, if integrated into or otherwise provided in an imaging device, may increase the size, complexity, and cost of the imaging device, which is undesirable especially for compact imaging devices. Furthermore, mechanical components such as motors and associated drive trains of mechanical shutters are more prone to wear and tear than solid state components such as a FPA, and thus adversely affect the overall reliability and longevity of imaging devices that rely on mechanical shutters.